1. Technical Field
The present disclosure relates to silicide formation, and more specifically, to methods of forming nickel silicide with fluorine incorporation and a related IC structure.
2. Related Art
Silicide is a metal-silicon alloy commonly used in complementary metal-oxide semiconductor (CMOS) technology for the purpose of, inter alia, providing a quality conductivity interface between silicon and metal contacts. Silicide may be formed by, e.g., performing an in-situ pre-clean, depositing a metal such as titanium, nickel, cobalt, etc., annealing to have the metal react with silicon, and removing unreacted metal using an etch.
Nickel silicide is a commonly used form of silicide. One challenge relative to the use of nickel silicide in CMOS technology, however, is that it can be unstable. For example, any defects in a silicon substrate crystal or in a source/drain region may lead to nickel silicide migration and, in particular, nickel migration, which can cause a large variety of defects such as nickel encroachments, fangs, opens, etc. The migration can occur during, for example, post-silicide formation processing such as anneals. One approach to prevent nickel migration is to incorporate fluorine in the nickel silicide, which increases the temperature at which the silicide becomes unstable (i.e., an agglomeration temperature) and reduces nickel migration. More specifically, the fluorine acts to fix the nickel in place, but does not impact silicide formation temperatures (Ni2Si or NiSi). Current techniques for incorporating fluorine into silicide all include ion implantation. In one case, the fluorine ion implantation is directed at the already-formed nickel silicide layer. This approach can create a lot of damage in the silicide due to the sputtering effect leading to defects, leakage, etc. In another case, the fluorine ion implantation is directed at the substrate upon which the silicide is later formed. In this situation, the fluorine presence in the substrate may be detrimental to the device later created therein, and may impact overall performance of the device.